Britney Spears celebrated the Fourth of July with a perfectly relaxing looking day out on the water in Marina del Rey, CA with her agent/recent vacation buddy Jason Trawick and some other friends. While Brit looks good taking it easy, there's yet another new rumor about a comeback project. The latest, taken with a big grain of salt, is a report that Britney will be collaborating with Madonna for a video to be played on the big screens during her upcoming Sticky and Sweet tour. Apparently, Britney would even join Madonna on stage at a few shows. I'm not sure if I buy this — and there have already been denials about performing together — but either way it would be a pretty great gig (and show of faith from Madonna) for Brit.